Within the context of the instant invention and in a preferred embodiment, a chip shaped carrier is a substrate, in particular a glass chip of e.g. squared shape having a thickness of e.g. 0.7 or 1.0 millimeter and a so called active surface, which is a surface coated with an array of different snippets of DNA or other molecular probes, e.g. DNA oligonucleotide probes, located at known positions on that surface. Those probes serve for detecting DNA fragments with a complementary DNA sequence.
Within the context of the instant invention and in a preferred embodiment the above-mentioned cartridge is in particular a cartridge made of a plastic material and used as a packaging device for packaging such a chip shaped carrier usually called DNA chip. More preferably, the cartridge is designed as a one-way cartridge.
DNA chips contained in such cartridges have a wide range of applications. For example, they may be used for understanding the structure-activity relationship between different biological materials or determining the DNA-sequence of an unknown biological material. For instance, the DNA-sequence of such unknown material may be determined by, for example, a process known as sequencing by hybridization. In one method of sequencing by hybridization, a sequences of diverse materials are formed at known locations on a surface of a chip, and a solution containing one or more targets to be sequenced is applied to that surface. The targets will bind or hybridize with only complementary sequences on the substrate. The locations at which hybridization occurs are detected with appropriate detection systems by labeling the targets with a fluorescent dye, radioactive isotope, enzyme, or other marker. Information about target sequences can be extracted from the data obtained by such detection systems.
By combining various available technologies, such as photolithography and fabrication techniques, substantial progress has been made in the fabrication and placement of diverse materials on chips of the above mentioned kind. For example, thousands of different sequences may be fabricated on a single substrate of about 1.28 square centimeter in only a small fraction of the time required by conventional methods. Such improvements make these substrates practical for use in various applications, such as biomedical research, clinical diagnostics, and other industrial markets, as well as the emerging field of genomics, which focuses on determining the relationship between genetic sequences and human physiology.
For efficient use of a chip shaped carrier of the above described type it is necessary that the sample solution containing one or more targets to be sequenced effectively contacts the active surface of the chip shaped carrier. Moreover, in view of the relatively large number of sample solutions to be processed, this effective contact should be achieved with high reproducibility and at low cost.
Known prior art attempts to attain these aims require means for pumping a liquid containing a nucleic acid sample into and out a chamber of a cartridge in order to obtain the desired effective contact between the liquid containing the sample and the active surface of the chip shaped carrier. This approach is too expensive, cumbersome and requires too much working space, and can therefore not satisfy present day requirements on this kind of apparatuses.
A main aim of the instant invention is therefore to provide a method, a cartridge and a system which make it possible to provide effective contact of a solution processed in a cartridge of the above mentioned kind with the active surface of the chip shaped carrier and this with a high reproducibility and at low cost.